The present invention relates to a rotary conveyor, more precisely relates to a rotary conveyor in which a rotating section can be turned without twisting and entangling electric cables, air tubes, etc.
In some conventional automatic machining lines, rotary conveyors are employed. The rotary conveyor intermittently conveys work pieces in a circumferential direction.
In the conventional rotary conveyor, a plurality of holding units, which are capable of respectively holding the work pieces, are provided in a rotating section with regular angular separations (an angle SA). The rotating section is intermittently turned the angle SA prescribed times so as to intermittently index and convey the work pieces. By employing the rotary conveyor, a plurality of steps for machining the work pieces can be executed simultaneously. The work pieces which have been completely machined are discharged in order. The rotary conveyor can efficiently machine the work pieces. Note that, the rotating section is intermittently and endlessly rotated in one direction only.
A wafer polishing machine disclosed in JP Pat. No. 2501763, which includes the conventional rotary conveyor, will be explained with reference to FIG. 3. The polishing machine polishes outer circumferential faces of wafers.
The polishing machine includes: a rotating section 50 capable of intermittently rotating a prescribed angle; a plurality of swing arms 51 being provided in the rotating section 50 with regular angular separations; a plurality of holding units 52, which are capable of respectively holding the wafers 60 and each of which is provided to a front end of each of the swing arms 51; a wafer loading station 53 which is located at a position corresponding to one of stop positions of the swing arms 51; a first polishing station 54 and a second polishing station 55 which respectively have rotary polishing units for polishing the wafers 60; a wafer unloading station 56; and swing drive units 57, which are respectively provided to the first and second polishing stations 54 and 55 and each of which turns the swing arm 51 located in the polishing station so as to press the outer circumferential face of the wafer 60, which has been held by the holding unit 52, to the rotary polishing unit. Note that, the holding units 50 include means for holding the wafers 60 by air suction, and the holding units 52 holding the wafers 50 can be rotated by rotary drive units 58.
However, in the conventional rotary conveyor, the rotating section is endlessly rotated in one direction only and electric devices and/or pneumatic devices are mounted on the rotating section, so slip rings and/or rotary joints must be required so as to prevent twisting and cutting electric cables and/or air tubes. Namely, the slip rings are used to maintain electric connection and the rotary joints are used to maintain air communication, even if the rotating section is endlessly rotated in the one direction only. By employing the slip rings and rotary joints, a structure of the conventional rotary conveyor must be complex.
Further, in the case of the conventional rotary conveyor for a complex machine, the number of poles of the slip rings must be limited, so a control unit including a sequence must be mounted on the rotating section.